Three to four million persons in the United States suffer from glaucoma to some degree, although only about half of these persons are treated by routine administration of glaucoma medication. Glaucoma is recognized to be the leading cause of blindness in this country.
Typical treatment for glaucoma to reduce the excessive intraocular pressure involves the administration of drugs which operate on the intraocular pressure. These drugs do not have a long term straight line effect on intraocular pressure, however, and individual treatments may be more or less effective at any particular period of time in the treatment cycle. For most glaucoma cases, intraocular pressure varies throughout the day, usually reaching its peak about 3:00 am. The diurnal cycle presents difficulties to the attending physician, who sees the patient at only one relatively short period of time. For this reason, it is difficult for the practitioner to accurately assess the effect of glaucoma medications. The only way this can be done economically is for the patient to make the measurements at home.
At the present time, there is recognition that the cycle of intraocular pressure is diurnal and is subject to several variables. However, no acceptable means presently exists to measure intraocular pressure at home with any degree of safety. The primary difficulty is that all prior art tonometers are designed to measure intraocular pressure through corneal indentation or corneal applination. This requires considerable skill and training along with anesthesia to the cornea.
Other methods such as air tonometry deflect the cornea with a burst of air. This method eliminates the need for anesthesia, but still requires considerable skill. The unit is quite costly and is not portable.
It is therefore an object of this invention to provide a portable tonometer which can be placed against the eye to record intraocular pressure by the patient without direct medical personnel supervision.
Another object of the present invention is to provide such a device which does not require anesthesia, and which is economical to manufacture and easy to use.
Yet another object of the present invention is to provide a device which can be used on the sclera of the eye to measure and record intraocular pressure and which has safety features to prevent too much pressure from being applied.
Other objects will appear hereinafter.